how to use group functionality in listview without using db?

<h3>ListViewh3>

<asp:ListView ID="lvCustomers" runat="server" GroupPlaceholderID="groupPlaceHolder1"

ItemPlaceholderID="itemPlaceHolder1" OnPagePropertiesChanging="OnPagePropertiesChanging">

<LayoutTemplate>

<table border="1">

<tr>

<th>Product

th>

<th>Quantity

th>

<th>Price

th>

<th>Category

th>

tr>

<asp:PlaceHolder runat="server" ID="groupPlaceHolder1">asp:PlaceHolder>

<tr>

<td colspan="3">

<asp:DataPager ID="DataPager1" runat="server" PagedControlID="lvCustomers" PageSize="2">

<Fields>

<asp:NextPreviousPagerField ButtonType="Link" ShowFirstPageButton="false" ShowPreviousPageButton="true"

ShowNextPageButton="false" />

<asp:NumericPagerField ButtonType="Link" />

<asp:NextPreviousPagerField ButtonType="Link" ShowNextPageButton="true" ShowLastPageButton="false" ShowPreviousPageButton="false" />

Fields>

asp:DataPager>

td>

tr>

table>

LayoutTemplate>

<GroupTemplate>

<tr>

<asp:PlaceHolder runat="server" ID="itemPlaceHolder1">asp:PlaceHolder>

tr>

GroupTemplate>

<ItemTemplate>

<td>

<%# Eval("Product_Name") %>

td>

<td>

<%# Eval("Quantity") %>

td>

<td>

<%# Eval("Price") %>

td>

<td>

<%# Eval("Category") %>

td>

ItemTemplate>

asp:ListView>